High aspect ratio light emitter having high uniformity and directionality

Abstract

A light emitter for emitting partially collimated light in one or more selected directions. The light emitter has a longitudinally specularly reflective internal surface; and, a light emitting area having an inner portion which is both partially longitudinally specular reflective and partially longitudinally transmissive and, a refractive, prismatic outer portion.

What is claimed is: 
     
       1. A hollow light emitter having a length considerably greater than its minimum cross-sectional dimension for receiving light from a partially collimated light source and emitting said light without substantial loss of collimation from a light emitting area of said emitter in one or more selected directions with substantially uniform light output per unit length along said light emitting area, said light emitter comprising: (a) a longitudinally specularly reflective internal surface;   (b) said light emitting area comprising: (i) an inner portion which is: (1) substantially longitudinally specularly reflective; and,   (2) longitudinally transmissive; and,     (ii) a refractive, prismatic outer portion separated from said inner portion by a gap.     
     
     
       2. A light emitter as defined in claim 1, wherein the degree of longitudinal transmissivity of said inner portion varies as a selected function of position on said inner portion. 
     
     
       3. A light emitter as defined in claim 2, wherein said transmissivity varies such that the quantity of light per unit area transmitted by said inner portion has a predetermined distribution of values as a function of position on the outer surface of said inner portion. 
     
     
       4. A light emitter as defined in claim 3, wherein said quantity of light per unit area transmitted by said inner portion is substantially uniform. 
     
     
       5. A light emitter as defined in claim 2, wherein said light emitting area is curved. 
     
     
       6. A light emitter as defined in claim 5, wherein said transmissivity varies such that the total luminous intensity of said emitted light has a predetermined distribution of values as a function of the direction of emission of said light. 
     
     
       7. A light emitter as defined in claim 6, wherein said total luminous intensity of said emitted light is substantially uniform. 
     
     
       8. A light emitter as defined in claim 6, wherein said total luminous intensity of said emitted light is substantially uniform within a selected directional range, and substantially zero outside said range. 
     
     
       9. A light emitter as defined in claim 6, wherein said transmissivity is varied such that the luminous intensity of said emitted light varies as 1/cos 2  θ over a selected range of θ, where θ is an angle measured relative to a preselected direction of emission. 
     
     
       10. A light emitter as defined in any one of claims 1 through 9, wherein light incident at any particular point on said outer portion is redirected into a direction substantially perpendicular to said outer portion at said point. 
     
     
       11. A light emitter as defined in any one of claims 1 through 9, wherein said outer portion transmits incident, collimated light in said selected direction with little or no loss of collimation. 
     
     
       12. A light emitter as defined in any one of claims 1 through 9, wherein said outer portion comprises transparent light extraction film having a structured surface and a second surface, said structured surface having a plurality of linear prisms thereon, each of said prisms having first and second sides, said first and second sides making an angle in the range of 59° to 79° with one another. 
     
     
       13. A light emitter as defined in any one of claims 1 through 9, wherein said inner portion comprises a transparent substrate bearing a metal pattern which varies as a selected function of position on said inner portion. 
     
     
       14. A light emitter as defined in any one of claims 1 through 9, wherein said outer portion comprises transparent light extraction film having a base layer defining a plane and having a structured surface, said surface having linear prisms thereon, each of said prisms having only four planar sides extending from said plane, two of said sides being adjacent said plane, the projections of which meet at a relatively narrow angle and two of said sides being more distant from said plane which meet at a relatively wide angle.